This invention relates to the art of reactive difunctional acid compounds.
Polybenzazole ("PBZ") polymers, such as polybenzoxazole ("PBO"), polybenzimidazole ("PBI") or polybenzothiazole ("PBT"), are a known class of polymers which are typically formed and fabricated in strongly dehydrating protic acid solvents. See e.g. Wolfe et al., Liquid Crystalline Polymer Compositions, Processes and Products, U.S. Pat. No. 4,533,693 (Aug. 6, 1985) and 11 Ency. Poly. Sci. & Eng., Polybenzothiazoles and Polybenzoxazoles, 601 (J. Wiley & Sons 1988).
In order to modify the properties of the PBZ polymers so that they will function adequately for various end use applications it is desirable to make copolymers of PBZ's and thermoplastic polymers. One such thermoplastic polymer is a polyarylethersulfone. See e.g. International Publication No. W090/03995 entitled Copolymers Containing Polybenzoxazole, Polybenzothiazole and Polybenzimidazole Moieties.
A strongly protic acid solvent/initiator medium is usually required for any type of polymerization with PBZ monomers, because PBZ polymers and copolymers require such an environment in order to react and remain in solution once formed. Therefore, in order to make copolymers of PBZ it is required that all reagents must be able to function in a strong protic acid solvent system.
Heretofore, such copolymers of PBZ's have been difficult, if not impossible to prepare, because of the lack of known reagents that were capable of reacting and remaining in solution in the strongly protic acid solvents required.